Color photography



Patented July is, 1939 COLOR. PHOTOGRAPHY Paul L. Salzberg, Wilmington,DeL, and Clayton F. A. White, Parlin, N. J., assignors to Du Pont FilmManufacturing Corporation, New York, N. Y., a corporation of Delaware NoDrawing. Application September 21, 1937, Serial No. 164,984

8 Claims. (o1. 95-6) This invention relates to photography and moreparticularly to photographic elements bearing emulsions which develop toform metallic silver and dyes in admixture with each other.

A principal object of this invention is to provide water insolubledye-forming bodies, hereinafter termed color-formers, which yield dyesby coupling with the oxidation products of photographic developingagents. A further object of the invention is to prepare multilayerphotographic films containing color-formers which do not migrate fromlayer to layer or from the film into the processing baths. Anotherobject of the invention is to prepare photographic emulsions containingdispersed therein such color-formers. A further object is to preparecolored photographs by employing such emulsions on either opaque ortransparent supports. Additional and more speciflc objects will plainlyappear from the detailed specification and claims presented herein inexempliflcation and not in limitation of the present invention.

It has already been proposed to incorporate with photographic emulsionscolor-formers which, in the presence of the oxidation products ofcertain photographic developing agents, form more or less insoluble dyesin situ with the metallic silver image. In subtractive multicolorphotography it is also known to coat multiple layers of emulsions,havingdiiferent color sensitivities, as monopack films. It hasalso beenproposed to incorporate in the individual emulsion layers of suchmonopacks dye-forming components which couple with the oxidationproducts of certain photographic developing agents to form more or lessinsoluble dyes.

Prior to the present invention it has been highly desirable that boththe-dye-forming components themselves, and the dyes thus formed, remainwithin the layer in which the dye-component was originally incorporatedand that at any stage in the life of the film, that they do not migrateor diffuse to another layer.

The above requirements are effectively obtained in the present novelinvention as will hereinafter be described.

be saturated or unsaturated, straight or branched 5 chain, and primary,secondary, or tertiary. Specific ethers that may be used are resorcinolmonon-dodecyl ether of the formula -oon,(om)won,

pyrocatechol-n-octadecyl ether of the formula 0 i(C 2)1uCHa resorcinolmono-8-n-pentadecyl ether of the formula resorcinolmono-n-9,10-octadecenyl ether, and pyrocatechol mono-6-(3,9-diethyl)tridecyl ether of the formula (C H2 2CH CzHa (airmen.

The alkoxy phenols of the above type may be prepared in any convenientmanner, as, for example, by condensing an ortho or meta dihydric phenolwith the appropriate alkyl halide. Resorcinol mono-n-dodecyl ether mayfor example be prepared as follows, parts given being by weight: Nineand five-tenths (9.5)

parts of potassium hydroxide and 20 parts of dry n-butyl alcohol aregently heated to boiling under reflux.

Twenty-one and five-tenths (21.5) parts of resorcinol dissolved in 48parts of dry n-butyl alcohol are added slowly with continued boiling,followed by 41.0 parts of n-dodecyl bromide, and 0.8 part of solidpotassium iodide. The reaction is allowed to continue with gentlerefluxing for twenty hours. The reaction vessel is then cooled; water isadded; and the butyl alcohol is distilled off. After cooling, a waxysolid layer appears, and the aqueous layer is decanted on. After washingand boiling with hot water until the solution shows a negative test forresorcinol, the solid mass is heated with a solution of 10 parts ofsodium hydroxide in 200 parts of water and 80 parts of ethyl alcohol.The mono ether passes into this solution leaving the diether as an oil.After separation and acidification of the aqueous layer withhydrochloric acid, the free resorcinol mono-n-dodecyl ether is obtainedas a semisolid mass. The crude product thus obtained is dissolved indiethyl ether, repeatedly washed with water and the diethyl etherallowed to evaporate ofl, whereupon the pure mono-n-dodecyl ether ofresorcinol is obtained by, vacuum distillation (B. P. 247 C. at 20 mm.).

The above described higher alkoxy phenols are incorporated inphotographic emulsions, for example, as follows:

To 100 cc. of 2% by weight aqueous gelatin solution is added a solutionconsisting of 8 cos. ethyl alcohol and 0.4 gram of the alkoxy phenol,e., g. the mono-n-dodecyl ether of resorcinol. The total weight of thecombined solutions is then brought to 150 grams with water, after whichthe mixture is added to 100 grams of a silver halidegelatino emulsion(which may or may not contain sensitizers) and mixed thoroughly. Thelatter emulsion is coated upon a suitable photographic support such aspaper or a cellulose derivative base, or upon another photographicemulsion layer which may or may not contain another color-forming dyecomponent. Alternatively, the silver halide emulsion may be coated on aplain or colored separating layer as one sensitive layer of a series ofsuch layers on a monopack, multilayered film for use in colorphotography.

After exposure directly in a camera or by printing through appropriatecolor records, the above film comprising at least one sensitive layercontaining a higher alkoxy phenol is developed by means of an alkalinesolution of p-phenylenediamine or its alkyl substituted derivatives suchas p-amino-dlrnethylor diethyl-aniline, whereupon the exposed silverhalides are reduced to metallic silver and insuluble blue-green dyes areformed in situ with the reduced silver due to the coupling of theoxidation products of the p-phenylene diamine developer, or its alkylsubstituted derivative, with the dihydric phenolic ether. Otherp-phenylenediamines whose oxidation products couple with thealkoxyphenol to form insoluble dyes may be used to develop the exposedsilver halide. It is necessary that one of the amino groups be primary;the other may be primary but should preferably be secondary or tertiary.

Besides the above use, these higher alkoxy phenols may also be appliedin color photography processes where auniformly-dyed layer containing asilver image is differentially bleached with respect to the amount ofsilver present. In such a case, either before or after the formation ofthe silver image with a developer whose oxidation products arenon-coupling with the colorforming dihydric phenolic ether, an overallbluegreen dye is formed in the emulsion layer by treating it with asolution of the direct oxidation product of the p-phenylene-diamine typeof developer such as p-nitroso-aniline, p-nitrosodimethyl-aniline,p-nitroso-diethyl-aniline, etc. After the layer of dye is formed, it isdifferentially bleached by treatment with a solution of stannouschloride and potassium bromide according to the process of Christensen.

The above described higher alkoxy phenols may also be incorporated ingelatin layers and sensitized by treatment with potassium or ammoniumbichromate. After appropriate exposure through a color separationrecord, the film may be developed in a p-phenylene-diamine type ofdeveloper whereupon the chromium oxides formed by the exposure oxidizethe developing agent and cause coupling with the alkoxy phenol to formblue-green dye images which need only washing to complete the coloredpicture. Another method is to develop the exposed bichromatcd colloidlayer containing the alkoxy phenol with hot water to remove the solublecolloid wherever it was not exposed and then to form a blue-green imageby treatment with p-nitroso-aniline or an alkylated p-nitroso-anilinederivative solution.

Among the characteristic advantages of the hlgh-mono-alkyl ethers ofdihydric phenols herein described are:

A. When incorporated in a given photographic layer they do not migrateor diffuse either in their dry state or when the film is subjected tobathing in water or alkaline solutions.

B. These compounds will react with the oxidation product of ap-phenylenediamine developer, as produced in the reduction of silverhalides, to form blue-green dyes of such color-absorption andtransmission characteristics as to make them particularly useful inmulticolor photography processes for the production of colored images.

0. The dyes thus produced do ,not tend to migrate nor diffuse aftertheir formation.

Inasmuch as the novel color-formers herein described are insoluble inwater and in the ordinary photographic processing baths, the excesscolor-forming bodies which have not entered into the dye-formationprocess therefore remain in the photographic layer in such a fine stateof division that they have not the slightest effect on quality of thefinished product. However, their presence in the. finished color picturemay be readily detected by suitable tests.

While the foregoing specification sets forth preferred exemplificationsof the present invention it is intended to include all variations andmodifications within the spirit and scope of the appended claims.

We claim:

1. A photographic emulsion comprising an alkoxy monohydric phenol inwhich the alkoxy group contains at least eight carbon atoms, and inwhich the para position to phenolic hydroxyl is unoccupied.

2. A color-forming photographic layer comprising a gelatino-silverhalide emulsion and an alkoxy monohydric phenol in which the alkoxygroup contains at least eight carbon atoms and in which the paraposition to the phenolic hydroxyl is unoccupied.

3. A color-forming photographic emulsion containing an alkoxymononuclear monohydric phenol in which the alkoxy group contains atleast eight carbon atoms and in which the para position to the phenolichydroxyl is unoccupied.

4. A color-forming photographic emulsion containing a mono alkyl etherof resorcinol in which '7. A color-forming photographic emulsion conthealkyl, radical contains at least eight carbon taining a mono-n-octadecylether of resorcinol. atoms. 8. A color-forming photographic emulsionc0n- 5. A color-forming photographic emulsion comtaining a mono-n-Q,10-0ctadecenyl ether of prising a gelatino-silver halide emulsioncontainres-orcinol. ing a mono-n-alkyl ether of resorcinol in which PAULL. SALZBERG. the alkyl radical contains at least 8 carbon atoms. CLAYTONF. A. WHITE.

6. A color-forming photographic emulsion containing a mono-n-dodecylether of resorcinol.

